Patent application WO-A-2005012765 describes a tensioner having a rigid, V-shaped fork including a vertex portion hinged to a fixed axis and a pair of free end portions supporting relative pulleys and cooperating respectively with a stretched section and a slack section of the belt.
When the drive is still, i.e. when the internal combustion engine is turned off, the tensioner remains in a position of static equilibrium determined by a tension which is basically uniform along the entire length of the belt.
During operation, the fork is rotated towards the stretched section via the action of the relative pulley, causing an increase in the average tension of the belt dependent upon the fork rotation and allowing tensioning of the slack section and therefore a correct operation of the drive.
In particular, it was demonstrated experimentally that the known tensioner causes relatively high tensions on the belt during operation and particularly when the internal combustion engine is starting up, thereby tending to overload the belt and the supports.